1. Field of the Invention
This invention relates to a new and improved fluidic control system for Turbines and, more particularly but not exclusively, to a new and improved fluidic control system for the precisely interrelated control of the speed and extraction (or inlet or exhaust) pressure of a steam turbine which operates in a process environment to drive a process compressor.
2. Description of the Prior Art
Although a variety of turbine control systems are known in the prior art which comprise fluidic components in the nature of pneumatic controllers to provide pneumatic speed and extraction pressure control signals for steam turbine speed and extraction pressure control valve positioning, it may be understood that such systems will generally be found to further comprise pluralities of mechanical linkages, levers and pivots and the like which are operable through mechanical movement to combine the pneumatic valve positioning signals into analog mechanical signals. These mechanical signals are then reconverted into proportional pneumatic valve positioning control signals which operate through appropriate servo mechanisms to position the turbine speed and extraction pressure control valves in accordance with the speed and extraction pressure demands placed on the turbine. The disadvantages of the prior art turbine control systems of this nature are believed well known to include the inherent wear, frictional, lost motion and non-linear characteristics of the mechanical system components which can detract from control system accuracy and which can render precise control system calibration, and/or adjustment to vary control system operational characteristics, difficult and time consuming. Too, the general proximity of the mechanical system components to the turbine can subject the former to heat and vibrational stress, can complicate turbine inspection and maintenance procedures, and can render protective isolation of the control system components more difficult. In addition, the necessity for conversion of pneumatic signals into analog mechanical signals and reconversion of the mechanical signals into pneumatic signals prior to the final signal conversion into mechanical form to operate the turbine control valves can, of course, function to introduce further inaccuracies to prior art control system operation.